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Science in international negotiations

The Climate Change Convention: a load of hot air?

By Peter Hulm

The IPCC consensus on climate change

The Intergovernmental Panel on Climate Change (IPCC) said that many climatologists believe that global warming as a result of the accumulation of trace gases in the atmosphere could raise the world's average temperature by 2°C within 50 years and mean sea-levels would rise by around 30-50cm by 2030 (McNeely, 1995, p 27, citing Warrick, 1988).

McNeely (1995:27) summarizes the degrees of consensus found by the panel as follows:




Basic characteristics

Fundamental physics of the greenhouse effect

Virtually certain


Added greenhouse gases add heat

Virtually certain


Greenhouse gases increasing because of human activity

Virtually certain


Significant reduction of uncertainty will require a decade or more

Virtually certain


Full recovery will require many centuries

Virtually certain

Projected effects by mid-21st Century


Large stratospheric cooling

Virtually certain


Global mean surface-precipitation increase

Very probable


Reduction of sea ice

Very probable


Arctic winter surface warming

Very probable


Rise in global sea-level



Local details of climate change



Tropical storm increases



Details of next 25 years


In this table,

Virtually certain means there is nearly unanimous agreement among scientists and no credible alternative view

Very probable means there is roughly a 90% chance of occurrence

Probable means there is approximately a 2/3 chance of occurrence

Uncertain means the evidence is lacking for the hypothesized effect




The scientific consensus

The problems of consensus

The politics of consensus

The threshold of danger

The politics of science

Knowledge-based communities


Buying scientific credibility

Science and the three paradigms

A utilitarian hypothesis

A cobweb model, modified


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11 December 2000 Webmaster